The present invention is specifically concerned with a problem encountered in trimming or punching relatively soft materials such as polypropylene or the like. In order to cleanly shear and trim the material, the punch should move rapidly through the material before the pressure applied to the material by the punch causes any significant amount of flowing of the material under the pressure applied. The speed of movement of the punch carrying platen in its operating stroke is subject to practical limitations, and with relatively soft or relatively easily compressed materials, the material will tend to flow or become deformed before the shearing stroke is completed, resulting in what is generally referred to as a smearing effect.
The present invention is designed to provide an instantaneous and temporary acceleration to the punch as it moves through the material being trimmed, with the objective of completing the shearing of the material before any substantial flowing or deformation takes place, and to accomplish this without requiring any acceleration or increased velocity of the relatively massive punch carrying platen.